Electronic states and magnetism of ultrathin Fe/Cu/Si(111) films

Epitaxial Fe/Cu/Si(111) ultrathin overlayers with Fe thicknesses ranging fr om 1 to 3 ML (monolayer) have been grown as well as a 30 ML thick iron film . The evolution of their electronic and magnetic properties next to the iro n fcc-bcc structural transition has been investigated by using several UHV techniques and compared to experimental results obtained for a completely b cc Fe/Cu heterostructure. For fee Fe coverages we found that at room temper ature the magnetic moment, m, is nearly zero contrary to that obtained by l ocal spin density calculations which reported for a surface iron layer an r n value even higher than in the bulk. Our measurements of electronic densit y of states suggest that the ultrathin film exchange splitting is even lowe r than that of bulk iron contrary to what is expected by theory. The observ ed decrease of the exchange splitting is not sufficient to explain the macr oscopic magnetic behaviour. (C) 2001 Elsevier Science B.V. All rights reser ved.